2. This period is about 5 times as long as the Paleozoic and Mesozoic combined, a very long time. Less is known about it than the younger time periods. The oldest fossils are of bacteria dating from 3 billion years ago (bya). The oldest rock is dated at 3.8 bya. The Earth is thought to be 4.6 bya. Periods within the Precambrian  PROTEROZOIC  ARCHEAN

3.  The Cambrian period, at the beginning of the Paleozoic, was the first time that multi-cellular life forms flourished on Earth. By the end of the Paleozoic, and beginning of the Mesozoic, all the continents of the Earth came together to form the giant continent called PANGAEA and dinosaurs began to roam on land. http://www.windows.ucar.edu/tour/link=/earth/geology/hist_pale ozoic.html Periods of the Paleozoic PERMIAN CARBONIFEROUS DEVONIAN SILURIAN ORDOVICIAN CAMBRIAN

4.  The Mesozoic is the period in which the dinosaurs lived, and its end was marked by the K-T extinction. This extinction event dramatically changed the Earth's flora and fauna, and its causes are still being investigated by scientists around the world. During the Mesozoic, the giant continent Pangaea broke apart into the continents we have today.  http://www.windows.ucar.edu/tour/link=/earth/ geology/hist_mesozoic.html http://www.windows.ucar.edu/tour/link=/earth/ geology/hist_mesozoic.html Periods of the Mesozoic CRETACEOUS JURASSIC TRIASSIC

5.  The beginning of the Eocene was a period when the Earth was very hot, with palm trees and alligators at the north pole. Earth but cooled by the start of the Quaternary. This period relates to today's concern about global warming. Homo sapiens evolved and Ice Ages occurs towards the end of this time. The Little Ice age (which is not a true ice age) occurred a few hundred years ago.  http://www.windows.ucar.edu/tour/link=/earth/geology/hist_ce nozoic.html http://www.windows.ucar.edu/tour/link=/earth/geology/hist_ce nozoic.html  Periods of the Cenozoic  HOLOCENE PLEISTOCENE PLIOCENE MIOCENE OLIGOCENE EOCENE PALEOCENE

6.  Cambrian 570 M-500 M Earliest Record of Marine life- Trilobites are dominantTrilobites  Ordovician 500M- 435 M EchinodermsEchinoderms ( Starfish, Sand dollar, sea urchin and sea cucumbers). Invertebrates are dominant, mollusks become abundant. Earliest Fish that are Jawless and later, jawed and armored fish.Invertebratesmollusks Fishjawed and armored fish.  Silurian 435 M- 395M Earliest terrestrial plants and animals. TiktaalikanimalsTiktaalik EurypteridsEurypterids develop  Devonian 395 M- 345M Armored fish go extinct, but abundance of several species of fish. Earliest amphibians and ammonites. fish.amphibiansammonites  Carboniferous 345M-280M (Mississippian, Pennsylvanian) Abundant sharks and amphibians. Large swamps and coal forming forests. Earliest reptiles. Scale trees and seed fernsreptilesScale trees seed ferns  Permian 280 M-225M Extinction of many types of marine animals including trilobites.

7.  Triassic- 225M-195M Earliest DinosaursEarliest Dinosaurs, abundant cycads and coniferscycadsconifers  Jurassic- 195M-136M Earliest birds Earliest birds and mammals abundant dinosaurs and ammonitesmammalsdinosaurs  Cretaceous- 136M-65M Earliest flowering plantsEarliest flowering plants, climax of dinosaurs followed by their extinction. Great decline of brachiopods. Abundance of bony fish. brachiopods

8.  Tertiary- 65 M- 1.8M Earliest Placental Mammals, modern mammals, large running mammals  Quaternary- 1.8 M – Present Large Carnivores, Neanderthals, Humans, mastodonsNeanderthalsHumans mastodons